The class of linear alternating polymers of carbon monoxide and at least one olefinically unsaturated compound is well known in the art. An early production of such polymers is shown by Nozaki, U.S. Pat. No. 3,694,412, wherein polymerization took place in the presence of arylphosphine complexes of palladium moieties as catalyst and certain inert solvents. More recent general processes for the production of the linear alternating polymers are illustrated by a number of published European Patent Applications including 121,965, 181,014, 213,671 and 257,663, as well as by U.S. Pat. Nos. 4,786,714 and 4,788,279. The processes generally involve a catalyst composition formed from a compound of palladium, cobalt or nickel, the anion of a strong non-hydrohalogenic acid and a bidentate ligand of phosphorus, arsenic, antimony, sulfur or nitrogen. The scope of the polymerization process is extensive but, without wishing to be limited, a preferred catalyst composition is typically formed from a compound of palladium, the anion of a non-hydrohalogenic acid having a pKa (measured in water at 18.degree. C.) of below 2 and a bidentate ligand, the choice of which may depend upon the particular unsaturated compound(s) being polymerized. For the polymerization of carbon monoxide and at least one ethylenically unsaturated acyclic hydrocarbon, the ligand is frequently a bidentate ligand of phosphorus.
Somewhat more difficulty is encountered when it is desired to form linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated compound when a cycloolefin is to be employed as reactant. In published European Patent Application 213,671 the use of cyclopentene and cyclohexene as the third monomer is disclosed in the production of terpolymers of carbon monoxide, ethylene and a third ethylenically unsaturated hydrocarbon. A similar disclosure is found in published European Patent Application 121,965. Processes that are useful in the production of a cycloolefin-containing terpolymer, however, are not always useful for the production of linear alternating copolymers of carbon monoxide and cyclic olefins. It would be of advantage to provide an improved process for the production of linear alternating copolymers of carbon monoxide and a cycloolefin, specifically a cyclopentene compound.